The outcomes of radiation therapy are often decided by the ability to deliver adequate dose to the tumor without also increasing dose to adjacent normal tissue which leads to unacceptable toxicity. For many patients, an effective strategy for increasing tumor dose is via stereotactic body radiotherapy (SBRT) and hypofractionated radiotherapy (HFRT). SBRT and HFRT may reduce the number of treatment sessions and enable better and more efficient cancer treatment. However, the application of SBRT and HFRT requires accurate patient setup and real-time image-based monitoring of patient/tumor position during treatment.
Dynamic adaptive radiotherapy (DART) opens a new era of cancer treatment. DART, as the name suggests, adapts dynamically to the ever-changing patient, and can adjust treatment delivery parameters in real time to correct for intrafractional motion and ensure that radiation is always aimed at the tumor rather than normal tissue. Application of DART also requires improved imaging for patient positioning and real-time tracking of the patient and tumor motion during treatment.
Radiation delivery machines such as LINACs have been equipped with electronic portal imaging devices (EPID) for acquisition of portal images to confirm patient setup. Existing EPIDs use megavoltage x-rays to provide 2D images but not 3D images. Further, existing MV imaging suffers from inferior image contrast and resolution, and requires higher dose than does kV imaging due to lower X-ray absorption of the devices at MV energies.
Accordingly, there is a need for electronic portal imaging devices capable of providing high-quality images using low-dose megavoltage x-rays. There is a need for imaging devices that are suitable for both kV and MV imaging and provides reliable 3D patient tracking in real time.